This project determines whether analogue or pulsatile cochlear implants provide better speech perception results in individual profoundly-deafened adults and whether the age at implantation is an important factor in the use of implants by prelingually-deafened children. We have shown that cochlear implants are a viable treatment for postlingually-deafened adults. However, there are large differences in the amount of benefit received by different patients. We have designed several investigations to evaluate the relative benefit of pulsatile and analog processing. In each of these investigations, we ask which of the two processing schemes results in higher speech perception scores. First, the two processing designs will be compared in 35 new patients using the Minimed implant. In one study they will alternate which processing strategy they use on a daily basis for the first four days of implant use. In a second study, they will alternate processors every 3 months, for the first year of implant use. Ten new subjects will be implanted with the Ineraid cochlear implant and will also alternate between the normal analogue processing of the Ineraid device and a new pulsatile strategy. They will follow the same protocol as the new Minimed users. Another study will examine whether cochlear-implant users with 18 months experience would benefit from a change in processors. Twenty-five patients who have used the Nucleus F1F2 cochlear implant will try the new Nucleus "minispeech" processor (MSP) for 3 months, then the original F1F2 for 3 months, and then the MSP again for 3 months. Twenty- five patients who have used the Ineraid cochlear implant will try the new pulsatile processor for 3 months, then the original Ineraid device for 3 months, and then the new pulsatile processor again for 3 months. In each study, a battery of speech perception tests will be administered whenever the patients changes processors. To determine the benefit of cochlear implants in prelingually-deaf children, 45 children will be studied in 3 groups of 15 children, according to the age that they received their cochlear implant: 2-5 years, 5-8 years, or 8-13 years. Scores will be compared across age groups when each subject has had 18 months of experience with their device, and when all subjects are 8 years or older and have their device for a minimum of 18 months.